Parametric Hull Design with Rational Bézier Curves and Estimation of Performances

In this paper, a tool able to support the sailing yacht designer during the early stage of thedesign process has been developed. Cubic Rational Bézier curves have been selected to describe themain curves defining the hull of a sailing yacht. The adopted approach is based upon the definition ofa set of parameters, say the length of waterline, the beam of the waterline, canoe body draft and somedimensionless coefficients according to the traditional way of the yacht designer. Some geometricalconstraints imposed on the curves (e.g., continuity, endpoint angles, curvature) have been conceivedaimed to avoid unreasonable shapes. These curves can be imported into any commercial ComputerAided Design (CAD) software and used as a frame to fit with a surface. The resistance of the hull canbe calculated and plotted in order to have a real time estimation of the performances. The algorithmand the related Graphical User Interface (GUI) have been written in Visual Basic for Excel. To test theusability and the precision of the tool, two existing sailboats with different characteristics have beensuccessfully replicated and a new design, taking advantages of both the hulls, has been developed.The new design shows good performances in terms of resistance values in a wide range of Froudenumbers with respect to the original hulls.